Flexible Porphyrinoids

Abstract

This review underscores the conformational flexibility of porphyrinoids, a unique class of functional molecules, starting from the smallest triphyrins(1.1.1) via [18]porphyrins(1.1.1.1) and concluding with a variety of expanded porphyrinoids and heteroporphyrinoids, including the enormous [96]tetracosaphyrin(1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0). The specific flexibility of porphyrinoids has been documented as instrumental in the designing or redesigning of macrocyclic frames, particularly in the search for adjustable platforms for coordination or organometallic chemistry, anion binding, or mechanistic switches in molecular devices. A structural prearrangement to coordinate one or more metal ions has been outlined. The coverage of the topic focuses on representative examples of geometry or conformational rearrangements for each selected class of the numerous porphyrinoids accordingly categorized by the number of built-in carbo- or heterocycles.

Mechanistic Study on Ring‐Contracting Skeletal Rearrangement from Porphycene to Isocorrole by Experimental and Theoretical Methods

“…There have been several reports on ring contraction of aromatic compounds in the field of porphyrinoids, 1) porphyrin to corrole contraction by the complexation of rhenium(V)[3a] or silver(III)[3b] 2) 21‐oxaporphyrin to 21‐oxacorrole contraction by the addition of phosphoryl chloride, 3) ring contraction from porphycene to meso ‐formyl isocorrole, 4) ring contraction of the expanded porphycene upon ruthenium metallation, 5) ring contraction of pyrihexaphyrin upon UO 2 + complexization, etc . However, such examples are limited and most of the reaction mechanisms of these unique reactions have not been revealed.…”

Helicenophyrins: Expanded Carbaporphyrins Incorporating Aza[5]helicene and Heptacyclic S‐Shaped Aza[5]helicene Motifs

“…Biphenylcorrole,closely related to phenanthriporphyrin, was afforded by replacement of the bipyrrole unit of corrole with ab iphenyl unit. [1,2,11] In the pursuit of expanded carbaporphyrinoids,a na pproach involving as ystematic, gradual incorporation of (E)-2-benzylidene-2H-pyrrole unit-(s) into the parent 1 is being explored. [9] In spite of the impressive exploration of the chemistry of expanded porphyrins,s tudies on expanded carbaporphyrinoids remain rather limited.…”

“…[4,11,[16][17][18][19][20] To define the structural factors stimulating intramolecular ring fusion of 4,m olecular modelling was used. Neither 3 nor 4 were detected in the mixture of products,i rrespective of the amount or type of oxidant used.…”

“…[9] In spite of the impressive exploration of the chemistry of expanded porphyrins,s tudies on expanded carbaporphyrinoids remain rather limited. [1,2,11] In the pursuit of expanded carbaporphyrinoids,a na pproach involving as ystematic, gradual incorporation of (E)-2-benzylidene-2H-pyrrole unit-(s) into the parent 1 is being explored. This formal expansion leads to the phenanthriporphyrinoids 2 NH and 3 as outlined at Scheme 1.…”

“…Evidently 4,f ormed initially in the condensation, underwent subsequent intramolecular oxidative ring fusion to yield the helicenophyrin 7 H2 .T he intramolecular ring fusion of porphyrinoids has been previously reported, and thus afforded the appropriate derivatives of an Nconfused porphyrin, 21-telluraporphyrin, and al arge variety of expanded porphyrins. [4,11,[16][17][18][19][20] To define the structural factors stimulating intramolecular ring fusion of 4,m olecular modelling was used. TheD FT-optimized model of 4 demonstrated af igure-of-eight conformation common for hexaphyrins, [11] with the benzene ring Ao fp henanthrene,a nd pyrrole Fring at the intersection ( Figure 1).…”